Friday, December 02, 2011

2002 review of Brooks/Hulme climate model paper: "It also shows many years in which rainfall approaches zero in the rainy season"; "The model results are extensively "massaged""; "I have no confidence in any of the conclusions draw from this simulation"

The model produces less than 50% of its rainfall in July, July, August, compared to about 80% in the "real world". It also shows many years in which rainfall approaches zero in the rainy season. The proper validation approach would have been to compare a 20th century simulation with the observed statistics. Further, it is important to show that the model can capture the mean spatial pattern and the real temporal variability of the observed data. This was not done. 2. The model results are extensively "massaged", using what appear to be arbitrarily chosen filters of 9 years, 25 years, 45 years, 96 years and 101 years. This is compared with unfiltered observational data. What is the justification of these particular filters, how do they affect the results. Is it appropriate to do statistical analyses, such as spectra, on the filtered series? 3. As a result of all of this statistical manipulation, it is difficult to follow what the authors do. It is even more difficult to judge their results and its statistical significance. This is particular problematic when a major results is correlations for thousands of grid points (Fig. 8.). If this work were to be revised, much more attention would have to be paid to the statistical approach and to validating the results. At the moment I have no confidence in any of the conclusions draw from this simulation.